1. Field of the Invention
The present invention relates to an image forming apparatus represented by a copying machine, a printer, and a facsimile machine.
2. Description of the Related Art
An image forming apparatus includes a sheet feeding cassette that can be pulled out from the apparatus main body and a manual tray (multi-purpose tray) can be opened and closed. A large number of frequently used standard sheets are stacked in the sheet feeding cassette. The standard sheets are separated one by one and fed toward a registration roller from the sheet feeding cassette.
Meanwhile, the manual tray is formed so that not only standard sheets but also special sheets, such as thick paper and post cards, can be stacked thereon. The sheets which are fed by manual operation are also separated one by one and sent toward the registration roller from the tray (see, for example, JP-A-2007-62917 and JP-A-2007-62966).
More specifically, when the manual tray is opened, a lifting plate provided to the tray abuts on a sheet feeding roller. A sheet is then manually placed on the tray. When the start button of the image forming apparatus is pressed, the sheet is nipped in a sheet feeding nip portion formed by the sheet feeding roller and the lifting plate that are pressed against each other. A feeding force is thus given to the sheet so that it is fed toward the registration roller.
Incidentally, there is a case where an opening is formed above the sheet feeding roller in the front side of the image forming apparatus facing the operator. For example, an image forming unit can be pulled out from the apparatus main body through this opening. It is therefore necessary for the image forming apparatus of this type to secure a space for the opening.
Meanwhile, the sheet feeding roller is supported on a multi-frame made of resin in a rotatable manner. Herein, when a pressure from the lifting plate acts on the sheet feeding roller, the multi-frame undergoes a deflection in a direction to escape from the lifting plate, which raises a problem that an appropriate sheet feeding force cannot be obtained. This problem can further cause jamming of the sheet at somewhere between the sheet feeding roller and the registration roller.
In order to solve this problem, the rigidity of the multi-frame may be enhanced with a reinforcing member, which is a separate member from the multi-frame, by attaching it to the multi-frame. According to this method, however, in pulling out a unit from the apparatus main body, a reinforcing structure interferes, and the operability worsens. In addition, because the number of components and the number of fabrication steps are increased, there arises another problem that the apparatus cannot be made cheaper.